Magnetic hysteresis of flux grown single crystals and melt grown YBa2Cu3O7−δ

Groot, Paj De; Beduz, C.; Zhu-An, YI; Ren, Yanru; Smith, S.W.

doi:10.1016/0921-4534(91)91360-g

Cited by 16 publications

(2 citation statements)

References 3 publications

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“…38,39 Because these regions were not directly observed, researchers suggested that twin boundaries trapped flux vortices and increased critical current densities. [38][39][40] Observations that a stronger fishtail effect occurred for samples with lower O content and higher densities of twin boundaries and that the fishtail effect was reduced in samples with low twin-boundary density were both consistent with that conclusion. 41 In light of our observations, we suggest a slightly different explanation.…”

Section: Resultssupporting

confidence: 83%

Structural inhomogeneity and twinning inYBa2Cu3O7−δsuperconductors: High-resolution transmission electron microscopy me

2008

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The superconducting properties of YBa 2 Cu 3 O 7-␦ ͑YBCO͒ are strongly dependent on atomic structure and composition. While the average structures of YBCO are well documented, the local oxygen concentration and ordering have received much less attention owing to the difficulty of experiments and analysis. We examined several samples of YBCO by quantitative high-resolution transmission electron microscopy and geometric phase analysis to determine their local atomic structure and symmetry. Our results reveal that adjacent domains separated by the ͑110͒ interfaces, commonly considered to be twin domains, can have different a o / b o ratios. The domains, therefore, do not retain the ideal twinned configuration commonly expected for this system. Assuming the a o / b o ratio is proportional to oxygen concentration, we suggest that these domains result from inhomogeneous oxygen distribution. Multiple measurements in both bulk and thin-film samples indicate that YBCO can consist of different phases, which may yield locally variable superconducting properties.

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Section: Resultssupporting

confidence: 83%

Structural inhomogeneity and twinning inYBa2Cu3O7−δsuperconductors: High-resolution transmission electron microscopy me

2008

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“…Oxygen-deficient zones have long been associated with the appearance of the fishtail pattern, nevertheless it has not been definitely proved whether or not they are responsible for the fishtail effect. In fact, 123 melttextured samples subjected to prolonged oxygenation show that fishtail patterns remain [114]. On the other hand, in other cases 123 melt-textured samples do not exhibit fishtail patterns either in the fully oxygenated or in oxygendeficient samples [115].…”

Section: Oxygenation Effectsmentioning

confidence: 99%

Tailoring of microstructure and critical currents in directionally solidified

Sandiumenge

Martı́nez

Obradors

1997

Supercond. Sci. Technol.

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Directionally solidified composites display a complex microstructure with several defects coexisting in the matrix and hence the identification of the flux-pinning mechanisms requires a detailed analysis of the critical currents. In this work we review the formation mechanism of twins, stacking faults, microcracks, subgrain boundaries and dislocations in connection with the refining strategies of (211 phase) inclusions and modifications of the microstructure generated through prolonged oxygen annealings and high-temperature plastic deformation of the ceramic. The influence of these defects and post-processing treatments on the critical currents is then analysed focusing on their relative importance as flux-pinning centres at different temperatures and magnetic fields up to 20 T. A complete magnetic phase diagram is finally proposed as a basis for a systematic classification of the observed irreversible superconducting behaviour in single-grain melt-textured composites.

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